Titolo !

1
Titolo !
MIT, November 21, 2003
One liquid, two glasses. The anomalous
dynamics in short ranged attractive colloids
Francesco Sciortino Email francesco.sciortino_at_p
hys.uniroma1.it
2
riassunto

• Outline of the talk
• The HS glass (and some comparisons with MCT
  predictions)
• How can we modulate the localization length in
  the glass ? Study short-range attractive colloids
  !
• -The MCT predictions for SW
• -Simulations
• -Experiments
• Glass-Glass ? Gels ? Hopping Phenomena ?

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HS e MCT
f(t)
HS (slow) dynamics

van Megen and S.M. Underwood Phys. Rev. Lett. 70,
2766 (1993)
4
Dati Thomas Giuseppe
Comparing MD data and MCT predictions for binary
HS
G. Foffi et al, PRE, in press
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MCT fq
BMLJ
SiO2
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HS
Hard Spheres
Potential
(No temperature, only density)
V(r)
r
s

• at h0.58, the system freezes forming disordered
  aggregates.

MCT transition ?51.6

1. W. van Megen and P.N. Pusey Phys. Rev. A 43, 5429
   (1991)
2. U. Bengtzelius et al. J. Phys. C 17, 5915 (1984)
3. W. van Megen and S.M. Underwood Phys. Rev. Lett.
   70, 2766 (1993)

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The MSD in HS
The mean square displacement (in the glass)
MSD
(0.1 s)2
log(t)
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What if .
Can the localization length be controlled in a
different way ?
What if we add a short-range attraction ?
Square-Well short range attractive Potential
Hard Spheres Potential
s
e
s D
lowering T
T gtgt e
T ltlt e
Attractive Glass
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Figure 1 di Natmat
A model with two different localization length
Mean squared displacement
repulsive
attractive
(0.1 s)2
D2
Log(t)
How does the system change from one (glass) to
the other ?
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The MCT predictions for short-range attractive
square well
MCT predictions for short range attractive
square-well
hard-sphere glass (repulsive)
Type B
s D
fluid
A3
Controlled by D/s
Short-range attractive glass
Fabbian et al PRE R1347 (1999) Bergenholtz and
Fuchs, PRE 59 5708 (1999)
Fluid-Glass on cooling and heating !!
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Non ergodicity parameters for the two glasses
Wavevector dependence of the non ergodicity
parameter (plateau) along the glass line
Fabbian et al PRE R1347 (1999) Bergenholtz and
Fuchs, PRE 59 5708 (1999)
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Isodiffusivity
Isodiffusivity curves (from MD BHS)
Zaccarelli et al PRE 2002
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Correlatori lungo la linea
Density-density correlators along the
iso-diffusivity locus
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Non-ergodicity factor
Non ergodicity parameter along the isodiffusivity
curve from MD
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R2 lungo la linea
Sub diffusive !
(0.1 s)2
D2
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Funzioni di correlazione
MD simulation
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Depletion Interactions Cartoons
Depletion Interaction A Cartoon
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Science Pham et al Fig 1
Fluid-glass line from experiments
Fluid samples
Glass samples
Temperature
MCT fluid-glass line
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Berths PRL (no polymer-with molymer)
HS (increasing f)
Adding short-range attraction
T. Eckert and E. Bartsch
T. Eckert and E. Bartsch
Colloidal-Polymer Mixture with Re-entrant Glass
Transition in a Depletion Interactions
Phys.Rev. Lett. 89 125701 (2002)
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Barsh PRL (phi effect)
Temperature
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Tracing the A4 point

• Tracing the A4 point
• Theory and Simulation

PY
PY transformation
fMD 1.897fPY-0.3922 TMD 0.5882TPY - 0.225
FS et al PRL in press
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Phi(t)
Same T and f, different D
Fq(t)fq-hq B(1) ln(t/t) B(2)q ln2(t/t).
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Phi hat

Fq(t)(Fq(t)-fq)/hq
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H(q)
FX(t)fX-hX B(1) ln(t/t) B(2)X ln2(t/t).
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MSD logaritmico
Slope 1
Slope less than 1
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Check List
Check List

• Reentrance (glass-liquid-glass)
• (both simulation and experiments)
• A4 dynamics v (simulation)
• Glass-glass transition

v
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Glass glass theory
low T
high T
t
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aging
Jumping into the glass
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Glass glass
The attractive glass is not stable !
low T
high T
Zaccarelli et al PRL 2003
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Bond No-bond
e
s D
t
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A summary
A summary

• Nice model for theoretical and numerical
  simulation
• Very complex dynamics - benchmark for microscopic
  theories of super-cooled liquid and glasses (MCT
  does well!)
• Model for activated processes
• Isochoric Diffusivity Maxima - PEL studies
  (saddles and Sconf) ?

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Fig 2 of Natmat
Summary 2 (and open questions) !
glass line
Repulsive Glass
Liquid
Non-adsorbing -polymer concentration
Temperature
?
Glass-glass transition
Attractive Glass
Activated Processes ?
Gel
Volume Fraction
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Pubblicita
Advertisement
       Structural Arrest Transitions in
Colloidal Systems  with Short-Range
Attractions   Messina, Italy, December 17
2003.   A workshop organized by Sow-Hsin Chen
(MIT) (sowhsin_at_mit.edu) Francesco Mallamace (U of
Messina) (mallamac_at_mail.unime.it) Francesco
Sciortino (U of Rome La Sapienza)
(francesco.sciortino_at_phys.uniroma1.it)   Purpose
To discuss, in depth, the recent progress on both
the mode coupling theory predictions and their
experimental tests on various aspects of
structural arrest transitions in colloidal
systems with short-range attractions.
http//server1.phys.uniroma1.it/DOCS/TAO/
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Equazioni base della MCT
Equations MCT !
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Explanation of the cage and analysis of
correlation function
The cage effect (in HS)
F(t)
Rattling in the cage
fq
Cage dynamics
log(t)